Skip to main content

Table 3 Multivariable logistic regression analyses for postoperative AKI according to increase in serum chloride levels (Cl)

From: Hyperchloremia and postoperative acute kidney injury: a retrospective analysis of data from the surgical intensive care unit

Group Variable Multivariable model 3
Odds ratio (95% CI) P value**
Entire sample (n = 7991) Increase in Cl, mmol L− 1*
 Q1: ≤ 1 mmol L− 1 1 (0.756)
 Q2: 1–3 mmol L− 1 0.84 (0.60, 1.18) 0.316
 Q3: 3–6 mmol L− 1 0.89 (0.66, 1.21) 0.456
 Q4: > 6 mmol L− 1 0.90 (0.66, 1.24) 0.528
Interaction of increase in Cl with eGFRa
 Increase in Cl: Q1 * eGFR: ≥ 90 1 (0.297)
 Increase in Cl: Q2 * eGFR: 60–89 1.04 (0.64, 1.70) 0.867
 Increase in Cl: Q2 * eGFR: 30–60 0.93 (0.60, 1.44) 0.738
 Increase in Cl: Q2 * eGFR: < 30 1.02 (0.60, 1.75) 0.934
 Increase in Cl: Q3 * eGFR: 60–89 0.93 (0.60, 1.44) 0.738
 Increase in Cl: Q3 * eGFR: 30–60 0.99 (0.63, 1.57) 0.973
 Increase in Cl: Q3 * eGFR: < 30 1.10 (0.67, 1.80) 0.702
 Increase in Cl: Q4 * eGFR: 60–89 0.92 (0.58, 1.46) 0.728
 Increase in Cl: Q4 * eGFR: 30–60 1.51 (0.95, 2.40) 0.084
 Increase in Cl: Q4 * eGFR: < 30 1.67 (1.01, 2.77) 0.045
  Four subgroup analysis Odds ratio (95% CI) P value***
eGFR ≥ 90 (n = 3437) Increase in Cl, mmol L− 1
 Q1: ≤ 1 mmol L− 1 1 (0.739)
 Q2: 1–3 mmol L− 1 0.84 (0.60, 1.19) 0.323
 Q3: 3–6 mmol L− 1 0.90 (0.66, 1.22) 0.491
 Q4: > 6 mmol L− 1 0.90 (0.66, 1.24) 0.529
eGFR < 90 (n = 4554) Increase in Cl, mmol L− 1
 Q1: ≤ 1 mmol L− 1 1 (0.023)
 Q2: 1–3 mmol L− 1 0.84 (0.68, 1.05) 0.123
 Q3: 3–6 mmol L− 1 0.88 (0.72, 1.07) 0.195
 Q4: > 6 mmol L− 1 1.16 (0.94, 1.41) 0.164
eGFR < 60 (n = 2201) Increase in Cl, mmol L− 1
 Q1: ≤ 1 mmol L− 1 1  
 Q2: 1–3 mmol L− 1 0.82 (0.61, 1.09) 0.164
 Q3: 3–6 mmol L− 1 0.90 (0.70, 1.17) 0.430
 Q4: > 6 mmol L− 1 1.42 (1.09, 1.84) 0.009
eGFR < 30 (n = 862) Increase in Cl, mmol/L
 Q1: ≤1 mmol L− 1 1 (0.068)
 Q2: 1–3 mmol L− 1 0.85 (0.56, 1.28) 0.428
 Q3: 3–6 mmol L− 1 0.94 (0.64, 1.40) 0.775
 Q4: > 6 mmol L− 1 1.48 (1.00, 2.21) 0.053
  1. Covariates with P < 0.2 on univariable analysis (see also Additional file 3) were included in the final multivariable model to adjust for potential confounders. Covariates for multivariable model 3 included preoperative American Society of Anesthesiologists (ASA) score, preoperative estimated glomerular filtration rate (eGFR), NaCl 0.9% and balanced crystalloid infused. The Hosmer-Lemeshow goodness-of-fit test was performed to investigate the fitness of the multivariable logistic regression models, and revealed no indication of lack of fit. Specifically, the Hosmer-Lemeshow statistic and P value, respectively, were 4.38 and 0.821 for the entire sample; 4.44 and 0.823 for the group of patients with eGFR ≥ 90 mL·min− 1·1.73·m− 2; 10.98 and 0.203 for the group of patients with eGFR < 90 mL·min− 1·1.73·m− 2; 11.92 and 0.155 for the group of patients with eGFR < 60 mL·min− 1·1.73·m− 2; 5.29 and 0.726 for the group of patients with eGFR < 30 mL·min− 1·1.73·m− 2
  2. AKI acute kidney disease, CI confidence interval, Cl serum chloride levels
  3. aPreoperative eGFR (mL·min− 1·1.73·m− 2) was calculated using the Modification of Diet in Renal Disease formula: 186 × (preoperative serum Creatinine)-1.154 × (Age)-0.203 (× 0.742 if female)
  4. *The increase in Cl was calculated as the difference between the preoperative value and the maximum value noted during postoperative days (PODs) 0–3. The following quartiles were obtained: Q1, 2535 patients (31.7%); Q2, 1593 patients (20.0%); Q3, 2075 patients (26.0%); and Q4, 1788 patients (22.4%)
  5. **P < 0.05 ***P < 0.012 (after Bonferroni correction) were considered to indicate statistical significance